1. Field of the Invention
The present invention relates to a swing motor reciprocated within a predetermined interval, and more particularly to a swing motor adapted to an appliance restricted in height by designing a motor structure with an asymmetric opening, preferably a semicircular opening formed inside a stator of a swing motor so as to accomplish reciprocation as well as to reduce the height of the swing motor.
2. Description of the Related Art
A conventional swing motor is described with reference to FIG. 1 as follows.
The conventional swing motor, as shown in FIG. 1, includes a stator 1, a rotor 2, and a spiral spring 3. The rotor 2 is installed inside the stator 1 in a state of being spaced apart from the stator 1, and is moved reciprocally by a magnetic field generated when an electric current is applied to the stator 1. The spiral spring 3 is connected to the rotor 2 to move the rotor 2 reciprocally.
In the conventional swing motor having a structure as described above, the rotor 2 moves reciprocally within a predetermined interval by using a resonant system of the spiral spring 3 like a linear motor.
The swing motor is formed with a space, called an opening, for disposing the rotor 2 inside the stator 1 in a state of being spaced apart from the stator 1. The opening is formed with salient poles facing the rotor 2.
Since the salient poles are wound with coils, a magnetic field is generated in the stator 1 when an electric current is applied to the coils.
The operation of the swing motor will be described with reference to FIG. 2 as follows.
FIG. 2 is a cross sectional view of the stator 1 of the swing motor. As shown in FIG. 2, the stator 1 is formed with a circular opening thereinside. The opening is formed with salient poles a, b, c, and d protruding toward the rotor 2.
Moreover, the salient poles a, b, c, and d are wound with coils to connect the salient pole a with the salient pole c, and to connect the salient pole b with the salient pole d.
When an electric current is applied to the coil connecting the salient pole a with the salient pole c, magnetic flux is generated in the direction A–A′. At this time, an N-pole is generated at the salient pole a while an S-pole is generated at the salient pole c.
When an electric current is applied to the coil of the salient poles b and d, a magnetic flux is generated in the direction B–B′. At that time, the salient pole b is magnetized to have an S-pole, and the salient pole d is magnetized to have an N-pole.
According to the conventional swing motor, in the case of applying electric current to the coils wound around the stator 1, the rotor 2 does not rotate, but moves in the directions A–A′ and B–B′ of the magnetic field generated by the applied electric current.
Thereby, the rotor 2 rotates clockwise by a predetermined angle when the magnetic flux is generated in the direction A–A′. After this, the rotor 2 returns to the initial position. The rotor 2 rotates counterclockwise by a predetermined angle when the magnetic flux is generated in the direction B–B′.
By repeating the above movements, the swing motor moves reciprocally within the predetermined angle without a mechanical device for transforming a rotational movement into a reciprocating movement.
However, to generate magnetic flux in desired directions, the conventional swing motor is provided with the salient poles, which are formed in the opening in the stator, facing the rotor. In this case, the salient poles have a symmetrical structure such as a circular shape.
Therefore, in the case of forming the salient poles symmetrically, the stator of the swing motor must have a predetermined height. If not, the symmetric salient poles may not be formed. For this reason, the volume of the swing motor is increased, and the miniaturization of the products installed with the swing motor has reached its limits.